Pharmaceutical compositions which include a medicament which is unstable in an acidic environment will require a basic excipient to enhance storage stability.
Pravastatin, an HMG-CoA reductase inhibitor disclosed in U.S. Pat. No. 4,346,227 to Terahara et al and having the formula ##STR1## is sensitive to a low pH environment and will degrade to form its lactone and various isomers.